First, I think it best to define the essence of the vampire (fictional) before attempting to define the Essence of the Vampyre (magical). In this way, I hope to invite discussion and/or debate on the topic, and to hear from other magicians' experience with this type of magic.
The word "essence," as defined by my Random House Dictionary, is "the basic intrinsic constituent or quality of a thing." It also means "the substance obtained from a plant or drug, by distillation or infusion, and containing its characteristic properties in concentrated form."
When examining the essence of the vampire, or that which is distilled once we remove various authors' character nuances and personalities, we find certain things in common in most every vampire story: the fact that a living victim had been bitten and killed by a vampire and is now basically a walking corpse with supernatural powers. These powers included turning into mist and shapeshifting, invisibility, mesmerism, superhuman strength, immortality and, of course, a murderous bloodthirst.
In 1819, Dr. John Polidori distilled even further the literary vampire's essence by replacing the ghoulish appearance with an aristocratic one. He further fashioned the personality of his vampire character after the infamous English Romantic poet, Lord George Gordon Noel Byron (1788-1824), for whom he had worked for a time and had grown to dislike by the time he wrote his story. Suddenly, the classic myth of the vampire had become something intriguing and sexually appealing to readers rather than horrific, and the beginnings of the Vampyric archetype was born.
Polidori was the first to utilize the new spelling of "Vampyre," and Polidori's main character, Lord Ruthven, also had the characteristic bloodthirst, as well as more elegant and appealing characteristics. Novelists from then on continued to utilize this breed of vampire in increasingly sexually oriented stories (including Bram Stoker's Dracula). Later, screen writers would develop this idea even further with the sensual movie version Dracula, starring Frank Langella.
For magicians, this Vampyric Essence can be experimented with in many ways. Distilled even further by removing the two remaining negative traits of the vampire, bloodlust and the animated corpse theory, we have an extremely sensual, sexual, aristocratic, magically and physically powerful Being. If one learns to emulate the powers of the vampire while keeping strongly in mind the intrinsic elegance and "Aristocracy of the Blood" that has developed within the archetype over the years, we now have the ingredients for a magical personality/persona known as the Vampyre.
How can these legendary powers be emulated? With only a little magic, imagination and dedication, it is quite easy, actually. "Superhuman" strength can be developed via weight training, using various strengthening and flexibility exercises. "Invisibility" can be learned by studying certain martial arts, such as Ninjutsu. "Shapeshifting" can be accomplished via pathworkings, trance states, and lycanthropic magic, as well as astral projection. Mesmerism can be learned by studying mesmerism and hypnotism, and also through psychology. The "Command to Look" can be practiced by experimenting with styles of dress and cosmetics, and via a projected Will.
Regarding immortality -- well, there are about as many beliefs regarding this as there are individual magicians. Some believe that immortality is achieved by strengthening the Will prior to Death. Some believe "psychic" or "life force" vampirism is necessary. Some believe that all human spirits are already immortal. Some believe all human psyches survive death, but then must know how to survive the "second" or "astral death." The method of this most alluring of the Vampyre's powers must be defined and explored by the individual magician according to their own studies.
Any of these traits taken alone for study and eventual perfection give on an interesting little power to add to their magical "arsenal." However, if one is truly studying the "awakening" of the Vampyric Essence and spends time developing each and all of these various talents, we have the makings of a very powerful magicians. Study never ends, of course, and each new "power" gives the magician just one more tool for self-awareness and evolution. This in turn strengthens the Vampyric talents, which again in turn empower the magician's evolution. This is the evolutionary Path of the Vampyre. (Complexities, and even dangers, of the Path beyond this simple description exist, of course, but are beyond the scope of this post.) The study of the Vampyric Essence is not for everyone. It is merely another Path for personal evolution. The concepts seem to resonate well with some personalities, while the image and archetype are abhorrent to others. Those on this particular magical Path tend to recognize one another, sometimes even before the other magician knows they would find this method intriguing. This is what is known as being "of the Blood." Vampyres tend to recognize kindred spirits.
Your individual Vampyric Essence is what you make of it. Each Vampyre, like each magician, is unique. The Vampyre may be seen as the next stage of human evolution, as the practice of magical Vampyrism (as opposed to vampirism) forces one to transcend common lower human traits and cultivate an aristocratic bearing, eloquence, and pride in Being.
The Path of the Vampyre is based on personal evolution. It's methods and trappings are sometimes Gothic-Victorian, though without the restriction and repression of these times in history. Emphasis is placed on the love of life, and conversely, the Understanding that Death is not to an experience to long for, but is merely a moment of great change. Vampyres tend to believe in immortality of the psyche, and live their lives based on this knowledge. And with this realization of the reality of continual evolution, an ever higher and exhalted state of Being is continually sought.